GRB 251011B
GCN Circular 42282
Subject
GRB 251011B: SVOM/VT optical upper limit
Date
2025-10-15T07:42:44Z (2 days ago)
From
Yinuo Ma <mayn@bao.ac.cn>
Via
Web form
Y. N. Ma, H. L. Li, Z. H. Yao, L. P. Xin, Y. L. Qiu, C. Wu, X. H. Han, Y. Xu, J. Wang, P. P. Zhang, W. J. Xie, Y. J. Xiao, H. B. Cai, L. Lan, J. S. Deng, J. Y. Wei, D. H. Zhao (NAOC), J. Palmerio (CEA), Y. H. Cheng (YNU), Y. Wang (PMO) report on behalf of the SVOM/VT team.
SVOM performed a Target of Opportunity observation of GRB 251011B detected by Swift/BAT, Fermi/GBM, and SVOM/GRM (D'Ai et al., GCN 42197; Fermi GBM team, GCN 42196; Evans et al., GCN 42201; Mukherjee et al., GCN 42204; Sbarufatti et al., GCN 42205; Zao et al., GCN 42206). SVOM/VT began observing the field at 2025-10-11 09:06:00 UTC, 1.961 hours after T0, in the VT_B (400nm-650nm) and VT_R (650nm-1000nm) channels simultaneously.
No uncatalogued sources, compared to Legacy Survey, were detected in our single or stacked images within the error box provided by Swift/XRT position (D'Ai et al., GCN 42197; Evans et al., GCN 42201), the three sigma limits are:
mid-time | exposure time | band | upper limit (AB)
----------|-----------------|-------|-----------------
2.3 h | 44*50 sec | VT_B | > 23.2 mag
2.3 h | 41*50 sec | VT_R | > 23.3 mag
Our results are consistent with MASTER (Balanutsa et al., GCN 42203) and Swift/UVOT (Siegel & D'Ai, GCN 42209).
The Space Variable Objects Monitor (SVOM) is a China-France joint mission led by the Chinese National Space Administration (CNSA, China), National Center for Space Studies (CNES, France) and the Chinese Academy of Sciences (CAS, China), which is dedicated to observing gamma-ray bursts and other transient phenomena in the energetic universe. VT was jointly developed by Xi'an Institute of Optics and Precision Mechanics (XIOPM), CAS and National astronomical observatories (NAOC), CAS.
GCN Circular 42211
Subject
GRB 251011B inspection: MASTER orphan GRB detection
Date
2025-10-13T00:15:06Z (4 days ago)
From
Vladimir Lipunov at Moscow State U/Krylov Obs <lipunov@xray.sai.msu.ru>
Via
email
Ya.Kechin, V.Lipunov, P.Balanutsa, A.Kuznetsov, G.Antipov, I.Panchenko, K.Zhirkov, E.Gorbovskoy, N.Tiurina, A.Sankovich, Ya.Kechin, M.Shilova, A.Chasovnikov, V.Topolev,
V.Senik, D.Vlasenko, Yu.Tselik (Lomonosov MSU),
R.Podesta, C.Francile, F. Podesta, E. Gonzalez (OAFA, San Juan Uni.,Argentina);
D.Buckley, (SAAO, South Africa)
O.Gress, N.Budnev (ISU, Irkutsk),
A. Sosnovskiy (CrAO RAS),
A. Tlatov, D. Dormidontov (Kislovodsk Solar Station of the Pulkovo Observatory),
A. Gabovich, V.Yurkov (Blagoveschensk Educational StateUniversity),
V.M.Pillet, R.Rebolo Lopez (The Instituto de Astrofisica de Canarias, Spain),
L.Carrasco, J.R.Valdes, V.Chavushyan, V.M.Patino Alvarez,J.Martinez,A.R.Corella,
L.H.Rodriguez (INAOE, Guillermo Haro Astrophysic Observatory, Mexico)
The MASTER-OAFA robotic telescope of the MASTER Global Robotic Net [1,2,3,4]
started Swift GRB 251011B
(Ttrigger=2025-10-11 07:08:22UT; XRT RA,Dec(2000)=00h 52m 56.33s,-62d 02'00.2" GCN 42197, GCN 42201)
alert observations at 2025-10-11 07:09:27 and observed it up to sunrise (Balanutsa et al. GCN 42203).
Next night MASTER automatic planner continued Fermi error-box (GCN 32196) inspection as independent alert
MASTER OT J011025.98-583210.6 discovery
MASTER-OAFA auto-detection system of MASTER Global Robotic Net [1,2,3,4]
during Fermi GRB 251011B (GCN42204, also detected by Swift (GCN42197) and observed by MASTER in alert mode (GCN 42203))
inspection discovered OT source at (RA, Dec) = 01h 10m 25.98s -58d 32m 10.6s on 2025-10-12.16208 UT
with light curve, that is typical for gamma-ray bursts optical counterpart.
The OT unfiltered magnitud m=17.8 (first image) at 2025-10-12 03:53:24UT (mlim=19.3 at single image).
The OT is seen in 8 images with typical GRB counterpart decay. There is no minor planet at this place.
We have reference image on 2025-09-16.19346 UT with unfiltered mlim=20.3m.
So as the Ttrigger for GRB 251011B was 19h earlier our discovery time (2025-10-11 07:08:22.33UT) and Swift error-box center was at 00h 52m 56.33s -62d 02' 00.2" (Swift GCN 42197, GCN 42201)
MASTER OT looks not connected with just GRB 251011B, but can be the orphan one [5].
Spectral observations and deep photometry are required.
[1] Lipunov et al., 2010, Advances in Astronomy, vol. 2010, 30L
[2] Lipunov et al. 2022, Universe, Vol. 8(5), id.271
[3] Lipunov et a. 2019, ARep, vol.63, 293
[4] Lipunov V., Kornilov V., Gorbovskoy E., Tiurina N., Kuznetsov A.
2023, Astronomical Robotic Networks and Operative Multichanel Astrophysics,Lomonosov MSU PRESS, 591pp.
http://www.pereplet.ru/lipunov/625.html#625
[5] Lipunov et al. 2022, MNRAS, 516, 4980 https://ui.adsabs.harvard.edu/abs/2022MNRAS.516.4980L/abstract
GCN Circular 42209
Subject
GRB 251011B: Swift/UVOT Upper Limits
Date
2025-10-12T15:56:51Z (4 days ago)
From
Mike Siegel at PSU/Swift MOC <mhs18@psu.edu>
Via
Web form
M. H. Siegel (PSU) and A. D'Ai (INAF-IASFPA)
report on behalf of the Swift/UVOT team:
The Swift/UVOT began settled observations of the field of GRB 251011B 107 s after the BAT trigger (D'Ai et al., GCN Circ. 42197). No optical afterglow consistent with the XRT position (Evans et al., GCN Circ. 42201) is detected in the initial UVOT exposures. Preliminary 3-sigma upper limits using the UVOT photometric system (Breeveld et al. 2011, AIP Conf. Proc. 1358, 373) for the first
finding chart (FC) exposure and subsequent exposures are:
Filter T_start(s) T_stop(s) Exp(s) Mag
white_FC 107 257 147 >20.9
white 107 257 147 >20.9
u 320 463 141 >20.4
The magnitudes in the table are not corrected for the Galactic extinction
due to the reddening of E(B-V) = 0.017 in the direction of the burst
(Schlegel et al. 1998).
GCN Circular 42206
Subject
GRB 251011B: SVOM/GRM observation
Date
2025-10-12T08:26:34Z (5 days ago)
From
xueyuan zao <zaoxueyuan@gmail.com>
Via
Web form
SVOM/GRM team: Xue-Yuan Zao, Zheng-Hang Yu, Chen-Wei Wang, Shi-Jie Zheng, Yue Huang, Shao-Lin Xiong, Shuang-Nan Zhang (IHEP)
SVOM/ECLAIRs team: Sebastien Guillot (IRAP), Stéphane Schanne (CEA), Nicolas Dagoneau
Report on behalf of the SVOM team:
SVOM/GRM detected the burst GRB 251011B at 2025-10-11T07:08:22.000 UTC (T0), which is also detected by Fermi/GBM (Fermi GBM Team, GCN #42196) and Swift/BAT (A. D'Ai et al., GCN #42197).
With the event-by-event data downloaded through the X-band ground station, we conducted the standard analysis pipeline of GRB 251011B. The GRM light curve shows that this burst consists of a single pulse with a T90 of 48 +9/-10 s in the 15-5000 keV band.
The SVOM/GRM light curve can be found here:
https://www.bursthub.cn//admin/static/svgrb251011B.png
In addition, the position of this burst, as determined by Fermi/GBM (RA= 5.3, DEC= -56.1, GCN#42196), is located at about 85.17 degrees from the SVOM optical axis, which is outside the ECLAIRs field of view.
With this localization, the time-averaged spectrum from T0-15 to T0+30 s is best fitted by a power law function. The power law index is 2.22 +0.23/-0.19. The event fluence (10-1000 keV) in this time interval is (3.56 +0.56/-0.82)E-06 erg/cm^2.
The Space Variable Objects Monitor (SVOM) is a China-France joint mission led by the Chinese National Space Administration (CNSA, China), National Center for Space Studies (CNES, France) and the Chinese Academy of Sciences (CAS, China), which is dedicated to observing gamma-ray bursts and other transient phenomena in the energetic universe. GRM is developed by the Institute of High Energy Physics (IHEP) of CAS.
The SVOM/GRM point of contact for this burst is: Xue-Yuan Zao (IHEP) (zaoxy@ihep.ac.cn)
GCN Circular 42205
Subject
GRB 251011B: Swift-XRT refined Analysis
Date
2025-10-12T07:29:18Z (5 days ago)
From
Phil Evans at U of Leicester <pae9@star.le.ac.uk>
Via
email
B. Sbarufatti (INAF-OAB), C. Salvaggio (INAF-OAB), S. Lanava (PSU), S.
Dichiara (PSU), J.A. Kennea (PSU), J.P. Osborne (U. Leicester), K.L.
Page (U. Leicester), A.P. Beardmore (U. Leicester), M. Ferro (INAF-OAB)
and P.A. Evans report on behalf of the Swift-XRT team:
We have analysed 5.1 ks of XRT data for GRB 251011B, from 85 s to 61.7
ks after the trigger. The data comprise 112 s in Windowed Timing (WT)
mode (the first 9 s were taken while Swift was slewing) with the
remainder in Photon Counting (PC) mode.
The light curve can be modelled with an initial power-law decay with an
index of alpha=3.12 (+/-0.08), followed by a break at T+579 s to an
alpha of 0.57 (+0.07, -0.20).
A spectrum formed from the WT mode data can be fitted with an absorbed
power-law with a photon spectral index of 2.15 (+/-0.12). The
best-fitting absorption column is 1.8 (+0.4, -0.3) x 10^21 cm^-2, in
excess of the Galactic value of 1.7 x 10^20 cm^-2 (Willingale et al.
2013). The counts to observed (unabsorbed) 0.3-10 keV flux conversion
factor deduced from this spectrum is 3.1 x 10^-11 (4.5 x 10^-11) erg
cm^-2 count^-1.
A summary of the WT-mode spectrum is thus:
Total column: 1.8 (+0.4, -0.3) x 10^21 cm^-2
Galactic foreground: 1.7 x 10^20 cm^-2
Excess significance: 8.4 sigma
Photon index: 2.15 (+/-0.12)
If the light curve continues to decay with a power-law decay index of
0.57, the count rate at T+24 hours will be 0.013 count s^-1,
corresponding to an observed (unabsorbed) 0.3-10 keV flux of 4.0 x
10^-13 (5.7 x 10^-13) erg cm^-2 s^-1.
The results of the XRT-team automatic analysis are available at
https://www.swift.ac.uk/xrt_products/01403191.
This circular is an official product of the Swift-XRT team.
GCN Circular 42204
Subject
GRB 251011B: Fermi GBM Observation
Date
2025-10-12T00:26:55Z (5 days ago)
From
oindabimukherjee@gmail.com
Via
Web form
O. Mukherjee (USRA), C. Meegan (UAH), U. Pathak (IIT Bombay) and L. Scotton (UAH) report on behalf of
the Fermi Gamma-ray Burst Monitor Team:
"At 07:08:21.91 UT on 11 October 2025, the Fermi Gamma-ray Burst Monitor (GBM)
triggered and located GRB 251011B (trigger 781859306/251011297).
which was also detected by Swift BAT (A. D'Ai et al. 2025, GCN 42197),
and Swift XRT (P.A. Evans et al. 2025, GCN 42201).
The Fermi GBM on-ground location is consistent with the Swift BAT position.
The angle from the Fermi LAT boresight is 81.8 degrees.
The GBM light curve consists of a single pulse with a duration (T90)
of about 35 s (50-300 keV). The time-averaged spectrum
from T0-8.0 to T0+26.5 s is best fit by
a Band function with Epeak = 36 +/- 5 keV,
alpha = 0.4 +/- 0.7, and beta = -2.2 +/- 0.1.
The event fluence (10-1000 keV) in this time interval is
(3.3 +/- 0.3)E-06 erg/cm^2. The 1-sec peak photon flux measured
starting from T0+0.58 s in the 10-1000 keV band is 3 +/- 0.2 ph/s/cm^2.
The spectral analysis results presented above are preliminary;
final results will be published in the GBM GRB Catalog:
https://heasarc.gsfc.nasa.gov/W3Browse/fermi/fermigbrst.html
For Fermi GBM data and info, please visit the official Fermi GBM Support Page:
https://fermi.gsfc.nasa.gov/ssc/data/access/gbm/"
GCN Circular 42203
Subject
GRB 251011B : MASTER optical observations
Date
2025-10-11T23:11:20Z (5 days ago)
From
Vladimir Lipunov at Moscow State U/Krylov Obs <lipunov@xray.sai.msu.ru>
Via
email
P.Balanutsa, V.Lipunov, A.Kuznetsov, G.Antipov, I.Panchenko, K.Zhirkov, N.Tiurina, A.Sankovich, Ya.Kechin, M.Shilova, A.Chasovnikov, V.Topolev,
V.Senik, D.Vlasenko, Yu.Tselik, E.Gorbovskoy(Lomonosov MSU),
R.Podesta, C.Francile, F. Podesta, E. Gonzalez (OAFA, San Juan Uni.,Argentina);
D.Buckley, (SAAO, South Africa)
O.Gress, N.Budnev (ISU, Irkutsk),
A. Sosnovskiy (CrAO RAS),
A. Tlatov, D. Dormidontov (Kislovodsk Solar Station of the Pulkovo Observatory),
A. Gabovich, V.Yurkov (Blagoveschensk Educational StateUniversity),
V.M.Pillet, R.Rebolo Lopez (The Instituto de Astrofisica de Canarias, Spain),
L.Carrasco, J.R.Valdes, V.Chavushyan, V.M.Patino Alvarez,J.Martinez,A.R.Corella,
L.H.Rodriguez (INAOE, Guillermo Haro Astrophysic Observatory, Mexico)
The MASTER-OAFA robotic telescope of the MASTER Global Robotic Net [1,2,3,4]
started GRB 251011B (Fermi GCN 42196, Swift: D'Ai et al. GCN 42197, XRT Evans et al. GCN 42201,
Ttrigger=2025-10-11 07:08:22UT XRT RA,Dec(2000)=00h 52m 56.33s,-62d 02' 00.2")
at 2025-10-11 07:09:27 with 10s expositions at 48 deg.altitude
There is no optical counterpart on a single images
Observations and reduction will be continued.
Tstart(+exp), UT RADec(2000) of MASTERsquarecent. Exp,s mlim
2025-10-11 07:09:07 00h 53m 53.80s -61d 58m 00.8s 10 18.0
2025-10-11 07:09:23 00h 53m 53.92s -61d 58m 00.0s 10 18.0
2025-10-11 07:09:39 00h 53m 53.86s -61d 58m 00.6s 20 18.6
2025-10-11 07:10:05 00h 53m 53.91s -61d 58m 00.5s 20 18.9
2025-10-11 07:10:31 00h 53m 54.05s -61d 57m 59.3s 30 18.0
2025-10-11 07:11:06 00h 53m 54.18s -61d 57m 59.2s 30 18.0
2025-10-11 07:11:43 00h 53m 54.30s -61d 57m 59.1s 40 18.3
2025-10-11 07:12:29 00h 53m 54.50s -61d 57m 58.5s 50 18.8
2025-10-11 07:13:25 00h 53m 54.74s -61d 57m 58.3s 60 19.2
2025-10-11 07:14:32 00h 53m 55.02s -61d 57m 57.6s 70 19.6
2025-10-11 07:15:47 00h 53m 55.39s -61d 57m 57.1s 90 19.6
2025-10-11 07:17:23 00h 53m 55.79s -61d 57m 56.7s 110 19.6
2025-10-11 07:19:19 00h 53m 56.33s -61d 57m 55.8s 130 19.6
2025-10-11 07:21:35 00h 53m 57.00s -61d 57m 55.1s 160 19.6
up to 2025-10-11 09:17:08.
[1] Lipunov et al., 2010, Advances in Astronomy, vol. 2010, 30L
[2] Lipunov et al. 2022, Universe, Vol. 8(5), id.271
[3] Lipunov et a. 2019, ARep, vol.63, 293
[4] Lipunov V., Kornilov V., Gorbovskoy E., Tiurina N., Kuznetsov A.
2023, Astronomical Robotic Networks and Operative Multichanel Astrophysics,
Lomonosov MSU PRESS, 591pp.
http://www.pereplet.ru/lipunov/625.html#625
GCN Circular 42201
Subject
GRB 251011B: Enhanced Swift-XRT position
Date
2025-10-11T14:07:46Z (5 days ago)
From
Phil Evans at U of Leicester <pae9@star.le.ac.uk>
Via
email
P.A. Evans, M.R. Goad, J.P. Osborne and A.P. Beardmore (U. Leicester)
report on behalf of the Swift-XRT team.
Using 243 s of XRT Photon Counting mode data and 1 UVOT
images for GRB 251011B, we find an astrometrically corrected X-ray
position (using the XRT-UVOT alignment and matching UVOT field sources
to the USNO-B1 catalogue): RA, Dec = 13.23469, -62.03340 which is equivalent
to:
RA (J2000): 00h 52m 56.33s
Dec (J2000): -62d 02' 00.2"
with an uncertainty of 2.4 arcsec (radius, 90% confidence).
This position may be improved as more data are received. The latest
position can be viewed at https://www.swift.ac.uk/xrt_positions. Position
enhancement is described by Goad et al. (2007, A&A, 476, 1401) and Evans
et al. (2009, MNRAS, 397, 1177).
This circular was automatically generated, and is an official product of the
Swift-XRT team.
GCN Circular 42197
Subject
GRB 251011B: Swift detection of a burst
Date
2025-10-11T07:29:21Z (6 days ago)
From
Antonino D'Ai' at INAF <antonino.dai@inaf.it>
Via
email
A. D'Ai (INAF-IASFPA), E. Ambrosi (INAF-IASFPA),
V. D'Elia (SSDC & INAF-OAR), R. Gupta (NASA GSFC),
N. P. M. Kuin (UCL-MSSL), A. Melandri (INAF-OAR),
K. L. Page (U Leicester), D. M. Palmer (LANL) and M. H. Siegel (PSU)
report on behalf of the Neil Gehrels Swift Observatory Team:
At 07:08:22.33 UT, the Swift Burst Alert Telescope (BAT) triggered and
located GRB 251011B (trigger=1403191). Swift slewed immediately to the burst.
The BAT on-board calculated location is
RA, Dec 13.287, -62.032 which is
RA(J2000) = 00h 53m 09s
Dec(J2000) = -62d 01' 55"
with an uncertainty of 3 arcmin (radius, 90% containment, including
systematic uncertainty). The BAT light curve showed a complex structure
with a duration of about 150 seconds. The peak count rate was ~3000
counts/sec (15-350 keV) at ~0 sec after the trigger.
The XRT began observing the field at 07:09:58.8 UT, 96.5 seconds after
the BAT trigger. Using promptly downlinked data we find a bright,
fading, uncatalogued X-ray source located at RA, Dec 13.23523,
-62.03269 which is equivalent to:
RA(J2000) = 00h 52m 56.46s
Dec(J2000) = -62d 01' 57.7"
with an uncertainty of 3.8 arcseconds (radius, 90% containment). This
location is 87 arcseconds from the BAT onboard position, within the BAT
error circle. This position may be improved as more data are received;
the latest position is available at https://www.swift.ac.uk/sper.
A power-law fit to a spectrum formed from promptly downlinked event
data gives a column density in excess of the Galactic value (1.68 x
10^20 cm^-2, Willingale et al. 2013), with an excess column of 4.5
(+3.47/-2.92) x 10^21 cm^-2 (90% confidence).
The initial flux in the 2.5 s image was 1.95e-09 erg cm^-2 s^-1 (0.2-10
keV).
UVOT data are unavailable at this time.
Burst Advocate for this burst is A. D'Ai (antonino.dai AT inaf.it).
Please contact the BA by email if you require additional information
regarding Swift followup of this burst. In extremely urgent cases, after
trying the Burst Advocate, you can contact the Swift PI by phone (see
Swift TOO web site for information: http://www.swift.psu.edu/)
GCN Circular 42196
Subject
GRB 251011B: Fermi GBM Final Real-time Localization
Date
2025-10-11T07:19:01Z (6 days ago)
From
Fermi GBM Team at MSFC/Fermi-GBM <do_not_reply@GIOC.nsstc.nasa.gov>
Via
email
The Fermi GBM team reports the detection of a likely LONG GRB
At 07:08:21 UT on 11 Oct 2025, the Fermi Gamma-ray Burst Monitor (GBM) triggered and located GRB 251011B (trigger 781859306.91454 / 251011297).
The on-ground calculated location, using the Fermi GBM trigger data, is RA = 5.3, Dec = -56.1 (J2000 degrees, equivalent to J2000 00h 21m, -56d 06'), with a statistical uncertainty of 5.3 degrees.
The angle from the Fermi LAT boresight is 78.0 degrees.
The skymap can be found here:
https://heasarc.gsfc.nasa.gov/FTP/fermi/data/gbm/triggers/2025/bn251011297/quicklook/glg_skymap_all_bn251011297.png
The HEALPix FITS file, including the estimated localization systematic, can be found here:
https://heasarc.gsfc.nasa.gov/FTP/fermi/data/gbm/triggers/2025/bn251011297/quicklook/glg_healpix_all_bn251011297.fit
The GBM light curve can be found here:
https://heasarc.gsfc.nasa.gov/FTP/fermi/data/gbm/triggers/2025/bn251011297/quicklook/glg_lc_medres34_bn251011297.gif